1. Field of the Invention
The present invention relates to a molding apparatus for molding a tubular elastic resin product such as a rubber stopper with a hollow axial interior. More particularly, the invention relates to a molding apparatus including an ejector pin for removing a tubular elastic resin product without damage from a mold.
2. Description of the Background Art
An example of tubular elastic resin products made by a conventional molding apparatus includes a rubber stopper 51 as shown in FIG. 14. The rubber stopper 51 has a hollow axial open interior 55, a uniform-diameter portion 60 to be held on one end of an outer peripheral surface thereof, and annular protrusions 59 having a smoothly curved surface and formed respectively in the middle of and on the other end of the outer peripheral surface thereof. The rubber stopper 51 is used to provide a water-tight seal between a terminal and a cable for an automotive vehicle and the like. The portion 60 of the rubber stopper 51 is held by a crimping portion of the terminal by crimping, with the cable received in the open interior 55, although not shown.
Referring to FIG. 16, the conventional molding apparatus for such a rubber stopper 51 includes a mold 57 having a vertically bored cavity 56 for molding the outer peripheral surface of the rubber stopper 51, and an ejector pin 50 for abutting against the end surface of the portion 60 of the rubber stopper 51 to release the rubber stopper 51 molded in the cavity 56 therefrom in an ejective manner. The ejector pin 50 is positioned above the mold 57 and is held by and suspended from a mold releasing plate 58 permitted to vertically move by a cylinder not shown and the like. The ejector pin 50 is finished into a cylindrical configuration with a uniform diameter throughout its length as shown in FIG. 15.
In the above described molding apparatus, as shown in FIG. 16, the rubber stopper 51 is molded in the cavity 56 and then released therefrom by moving the mold releasing plate 58 downwardly by the cylinder not shown and the like. This causes the lower end of the ejector pin 50 to abut against the upper end surface of the portion 60 of the rubber stopper 51. As the ejector pin 50 further moves downwardly in the cavity 56, the rubber stopper 51 is released in such a manner that the rubber stopper 51 is forced downwardly out of the cavity 56 as shown in FIG. 17.
Unfortunately, the rubber stopper 51 molded by the conventional molding apparatus has the portion 60 of cylindrical configuration and is hence disadvantageous in that the terminal crimped to the portion 60 is easily slipped axially off the portion 60. To overcome the disadvantage, a new rubber stopper 28 has been proposed which has an annular edge portion 26 bulged outwardly from the end of the portion 60 of the rubber stopper 28 as shown in FIG. 18. The rubber stopper 28 is mounted to one end of a cable 30, and a crimping portion 32 of a terminal 29 is crimped to the portion 60 as shown in FIG. 19. This allows the annular edge portion 26 to lock the crimping portion 32, preventing the terminal 29 from being slipped off the rubber stopper 28.
However, when the rubber stopper 28 having the annular edge portion 26 is molded by the mold 57 having an annular edge portion molding portion 54 at the upper end of the cavity 56 and of a recessed annular configuration complementary in shape to the annular edge portion 26 and is then released from the mold 57 by the cylindrical ejector pin 50 as shown in FIG. 20, a crack 53 is produced in the base portion of the annular edge portion 26 as shown in FIGS. 21 and 22.
More specifically, as shown in FIG. 21, when the lower end of the ejector pin 50 abutting against the end surface of the annular edge portion 26 of the rubber stopper 28 is moved downwardly, the periphery of the open interior 55 of the rubber stopper 28 is forced downwardly by the ejector pin 50, with the annular edge portion 26 locked in the annular edge portion molding portion 54. Then a tearing force is strongly exerted on the base portion of annular edge portion 26 to produce the crack 53 in the base portion thereof (FIG. 22).